PURPOSE: To reduce the labor and shorten the construction period of the building of a concrete structure, and improve the durability of the concrete structure to be built.

CONSTITUTION: Timbering frames 20 are attached to a surface 10a of a PCa concrete board 10 through connecting means 30 for separators 40, and the PCa concrete boards 10 are connected oppositely to each other through the separators 40 to assemble a form 1 so that concrete is placed in a space S between the oppositely disposed boards 10. And after the lapse of a specific time after the placing of concrete, the timbering frames 20 are removed from the boards 10.